The present invention relates to a laser surveying instrument to measure multiple points in regard to an object to be measured at a high speed and to acquire point group data.
To acquire three-dimensional data of the object to be measured, the point group data in regard to the object to be measured is acquired. As one of measuring devices which acquire the point group data, there is a laser scanner. For example, Japanese Patent Application Publication JP-A-2008-76303 discloses a laser scanner comprising a deflection mirror which rotates around a horizontal axis in an elevation direction and also rotates around a vertical axis in a horizontal direction and a light projecting optical system which has an optical axis coinciding with the vertical axis and projects a pulsed distance measuring light to the optical axis.
In the laser scanner, the pulsed distance measuring light emitted from the light projecting optical system is subjected to a reciprocating scan in the elevation direction at a predetermined angle by the deflection mirror, the deflection mirror is rotated to project the pulsed distance measuring light in a total circumferential direction, a reflection light of the pulsed distance measuring light is received to perform a distance measurement for every pulsed distance measuring light, thereby acquiring the point group data in regard to the total circumferential direction.
Further, the laser scanner is mounted in a moving object such as an automobile together with an image pickup device, and the laser scanner acquires an image and the point group data while moving to acquire an image with the three-dimensional data. Furthermore, in order to enable the more precise and more real modeling, the density growth of the point group data is demanded.
Alternatively, considering a situation that a trouble occurs in the measurement, e.g., that an obstacle such as an automobile blocks a laser during the measurement, a further increase in speed for acquiring the point group data has been demanded.
The current demand for an increase in speed for acquiring the point group data is met by increasing in light emission frequency of a light-emitting diode which emits a pulse and by realizing high-speed rotation of a deflection mirror which scans a pulse laser.
However, it cannot be said that the demand for an increase in speed is sufficiently met because of a limit of an increase in the light emission frequency due to a light emission duty ratio of the light-emitting diode, and because of a limit of a reduction in weight of the deflection mirror and a limit of an increase in speed of a driving motor, and others. Moreover, to meet the demand for the increase in speed, an increase in cost is an obstacle because a high-quality light-emitting diode is required and an increase in speed of a driving mechanism for the deflection mirror should be satisfied, for example.